import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import javax.swing.*;

public class ChatClientFrame extends JFrame {
  
  private JTextArea textArea;
  private Action send;
  private JTextField inputField;
  public ChatClientFrame(String title) {
    
    super(title);
    
    textArea = new JTextArea();
    textArea.setEditable(false);
    textArea.setLineWrap(true);
    
    send = new AbstractAction("Send") {

      @Override
      public void actionPerformed(ActionEvent e) {
        
        String message = inputField.getText();
        inputField.setText("");
        // ... send message logic
      }
    };
    
    inputField = new JTextField();
    
    layoutComponents();
    pack();
  }
  
  private void layoutComponents() {
    
    textArea.setPreferredSize(new Dimension(500, 500));
    JScrollPane center = new JScrollPane(textArea);
    center.setBorder(BorderFactory.createCompoundBorder(
            center.getBorder(),
            BorderFactory.createEmptyBorder(5, 5, 5, 5)));
    
    FlowLayout layout = new FlowLayout(FlowLayout.LEFT);
    JPanel south = new JPanel(layout);
    
    JButton button = new JButton(send);
    int width = center.getPreferredSize().width - 
                button.getPreferredSize().width -
                (layout.getHgap() * 3);
    
    int height = button.getPreferredSize().height;
    
    inputField.setPreferredSize(new Dimension(width, height));
    
    south.add(inputField);
    south.add(button);
    
    getContentPane().add(center, BorderLayout.CENTER);
    getContentPane().add(south, BorderLayout.SOUTH);
  }
  
  public static void main(String[] args) {
    
    SwingUtilities.invokeLater(new Runnable() {

      @Override
      public void run() {
        
        JFrame f = new ChatClientFrame("Chat Client");
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
      }
    });
  }
}